A computer implemented method of generating a new three-dimensional morphable model (3DMM) by combining a first 3DMM with a second 3DMM includes generating, using the first 3DMM, a plurality of first shapes, calculating a mapping from a plurality of second parameters of the second 3DMM to a plurality of first parameters of the first 3DMM, generating, for each of a plurality of second shapes generated using the second 3DMM, a corresponding first shape, forming a plurality of merged shapes by merging each second shape with the corresponding first shape, and performing principal component analysis on the plurality of merged shapes to generate the new 3DMM.